Grinding machine for machining polygonal workpieces

ABSTRACT

The invention concerns a grinding machine whereby diverse polygonal workpieces may be ground in a manner similar to conventional roll grinding and internal grinding. In the machine according to the invention the workpiece to be ground is rotated about its axis, a grinding tool is rotated about its own axis which is parallel with the workpiece axis and which is stationary or alternatingly rotating, and at the same time the axis of the workpiece is rotated around the periphery of a cylinder of rotation - whose axis is parallel with the workpiece axis - at an r.p.m. practically equal to the r.p.m. of the workpiece about its own axis multiplied by the number of sides of the polygon and the ratio of the angular velocities of the first two above-mentioned rotations is periodically changed.

United States Patent [191' Tajnafiii et al.

GRINDING MACHINE FOR MACHINING POLYGONAL WORKPIECES Inventors: Jzsef Tajnafiii; Keiroly Gellrt;

Karoly Hidasi; Laszld Gribovszki; Sandor Vkony, all of Miskolc, Hungary Assignee: Nehezipari Muszaki Egyetem,

Miskolc-Egyeternvaros, Hungary Filed: Apr. 9, 1974 Appl. No.: 459,378

Foreign Application Priority Data Apr. 24, 1973 Hungary NE 509 U.S. Cl 51/105 EC; 51/97 NC; 51/33 W; SI/DIG. 32

Int. Cl B24b 5/16 Field of Search 51/32, 33 W, 50 R, 90, 5l/95 Wl-I, 97 R, 97 NC, 105 R, 105 EC,

287 R, DIG. 32; 82/18 References Cited UNITED STATES PATENTS l/l939 Mossdorf 51/97 NC 12/1941 Mossdorf 51/95 WH 1 June 3, 1975 2,909,010 10/1959 Zelewsky .1 51/90 3,593,603 7/1971 Gellert ..82/18 3,623,272 11/1971 Flid et al. 51/105 R Primary ExaminerDonald G. Kelly Assistant Examiner-K. J. Ramsey Attorney, Agent, or FirmYoung & Thompson [5 7 ABSTRACT The invention concerns a grinding machine whereby diverse polygonal workpieces may be ground in a manner similar to conventional roll grinding and internal grinding.

In the machine according to the invention the workpiece to be ground is rotated about its axis, a grinding tool is rotated about its own axis which is parallel with the workpiece axis and which is stationary or alternatingly rotating, and at the same time the axis of the workpiece is rotated around the periphery of a cylinder of rotation whose axis is parallel with the workpiece axis at an r.p.m. practically equal to the r.p.m. of the workpiece about its own axis multiplied by the number of sides of the polygon and the ratio of the angular velocities of the first two above-mentioned rotations is periodically changed.

5 Claims, 33 Drawing Figures PATENTEDJUHB 1915 3886693 SHEET 2 FATHHEUJUf-I SHEET Fig.9

Fig.10

PATENTEDJUHB m5 SHEET Fig.17

PATEIHEDJUZi 3 I975 SHEET Fig. 24

PATENTEDJUHB 1915 33867693 SHEET 15 SHEET Fig.32

GRINDING MACHINE FOR MACHINING POLYGONAL WORKPIECES The invention concerns a grinding machine whereby diverse polygonal workpiece may be ground in a manner similar to convention roll grinding and internal grinding.

In the field of manufacture of machines, vehicles and mass production the demand arises ever more frequently to form workpieces for performing certain tasks in a polygonal shape. Polygonally shaped workpieces are particularly suitable e.g. for connecting shafts and components coupled thereto, for performing shape-determining tasks of mass production, tools, stamping tools and the like and for control tasks etc. Although their use affords great technical and economic advantages, their general reduction to practice has so far in many cases run into obstacles.

The major part of the obstacles has hitherto been the absence of a process and apparatus enabling the efficient, sufficiently accurate and economic production of a polygonal workpiece ground both externally and internally in a way similar to e.g. a shaft produced on a traditional machine tool.

A further obstacle to the rapid growth of use has also been the fact that the shapes and dimensions of polygonal workpieces required in industry may vary widely and in the hitherto known processes and apparatuses the change-over from one shape and one set of dimensions to another has meant a lot of time and considerable assembly work.

The wider use of polygonal workpieces has also been hindered by the fact that the hitherto known machines and devices used for their production had not been rigid enough to resist the rotational movements and translational circular movements (planetary movements) and elliptical movements giving rise to relatively large force effects without change of shape or wear; and after a relatively long operational life they could not ensure the specified dimensional accuracy, or alternatively in order to achieve the necessary rigidity, it has been necessary to build very robust and expensive machines and to limit the speeds of the movement which had an unfavourable effect on productivity.

To machine the exterior and interior surfaces of polygonal workpieces in a manner akin to turning there is already known a process and apparatus which can produce workpieces at a quality of grade IT 8, dimensionally accurately and true to the desired shape (Hungarian Patent Specification No. 156,607). To produce greater dimensional accuracy, better trueness of shape and higher surface quality one must employ grindingtype machining; however, between the tools of turning and grinding there are such differences in shapes, sizes and drive mechanisms that it is not possible to produce polygonal workpieces machined on the external and internal surfaces by copying a process and machine employed in turning.

In the hitherto known processes for grinding the external surfaces of polygonal workpieces great problems have arisen.

In many known processes a difficulty is caused by the fact that the movement of the large-mass grinding wheel, spindle, sheaves, headstock etc., caused by a lever mechanism generated considerable dynamic forces; in addition the headstock must movein synchronism with the movement of the workpiece which is difficult to achieve and which from the points of view of accuracy of working, wear and service life of the machine causes difficulties.

In one known process a difficulty is caused also by the use of elliptical motion in place of planetary motion in order to eliminate errors stemming from changes in diameter of the grinding disc. The motion is obtained by the superposition of two mutally perpendicular linear components of movement. This motion may be generated e.g. by means of an eccentric, wherein the horizontal component of the eccentric movement is transmitted to the rotary shaft of the grinding disc by a push rod and the vertical component by a two-armed lever. The lever arm ratio of the two-armed lever is adjustable, which makes it possible to change the circular motion into a movement along an elliptical path. The transmission to the grinding disc of the two components of movement set the requirement on the grinding disc that it should be journalled in a complicated system of positive constraints made up of the following parts: i

The grinding shaft is journalled in main bearings. The main bearings are displaceable in vertical, linear guides. The linear guides are carried by a body which is displaceable in horizontal guides.

The horizontal guides are formed in a grinding slide which can be regarded as rigid enough.

Thus in this known system, the large-mass grinding disc rotating at about 3000 r.p.m. moves in a serially connected, weak constraint system, with a period corresponding to the number of sides of the polygon, for each rotation of the workpiece. This circumstance leads to the creation of large dynamic forces.

It occurs in the course of using polygonal workpieces that for an already existing workpiece machined on its external or internal surface, a suitable pair of workpieces is required to be made, and the already existing and the new workpieces have to be interfitted in accordance with the given requirements. This means in essence that one must be able to grind polygonal profiles, characterised by the given polygonal number and by the maximum and minimum radii, along differently profiled curves.

Some of the known processes and grinding machines also suffer from the fault that wear of the grinding disc greatly influences the trueness of shape and dimensional accuracy of the workpiece produce, and neither the auxiliary movements in the directions of feed and rotation, nor the main machining movement always be set to the optimum value.

The invention seeks to provide a grinding machine for the machining of polygonal workpieces by means of which both the external and the internal surfaces of workpieces can be finish-machined with a dimensional accuracy equal to that of traditional grinding processes; the workpieces belonging together and pushed into each other have external and internal surfaces which fit togehter along practically the whole of their circumference, during machining the generated dynamic forces are smaller by an order of magnitude than those in known solutions, the change-over from one polygonal shape to another of different dimensions and configuration can be effected quickly and easily, wear of the grinding disc has practically no influence on the trueness of shape and on dimensional accuracy, the auxiliary movements in the directions of feed and cut, as well as main machining movement may be optimised for the machining requirements at all times, furthermore the machine or construction used for grinding has few components, is not liable to breakdown, is rigid, and in addition affords the possibility of fitting ground workpieces to workpieces of a given polygonal shape fabricated by another process, by virtue of the fact that a polygonal profile characterised by a given polygon number and by maximum and minimum radii can be ground with differently profiled curves.

With the invention the task set is solved by rotating the workpiece to be ground about its own axis which is parallel with the axis of a grinding disc or ring which has either a stationary axis or an alternatingly moving axis, and at the same time the axis of the workpiece is rotated along the periphery of a cylinder of rotation with an axis parallel with axis of the workpiece, the number of revolutions being equal to the number of revolutions of the workpiece about its own axis multiplied by the number of sides of polygon, and the ratio of angular velocities of the former fundamental motions is periodically changed.

A further characteristic is that in the course of machining the internal surfaces, the shaft of the stone carrying out the machining and rotating about its own axis is displaced together with an arm performing an angular or linear movement about the axis of the grinding disc or ring carrying out the machining of the external surfaces, and the distance between the stationary shaft of the grinding disc or ring operating on the outer mantle and the point on the periphery of the stone farthest or nearest to the shaft is kept equal to the radius of the grinding disc or ring operating on the outer surface.

A further characteristic of the invention is that in the course of machining both half-sections of each side of the polygonal workpiece, from the starting point of a half-section the angular velocity of the planetary movement of the workpiece is continuously changed to a maximum value, then by changing the sign of the change of angular velocity the change in angular displacement stemming from the change in angular velocity is continuously reduced to the end of the halfsection.

Another characteristic of the the invention is that during machining the workpiece is rotated about its own axis and the shaft of the workpiece is rotated in the same or in the opposite direction along the periphery of the cylinder of rotation.

The grinding machine according to the invention is characterized in that it has: a main spindle rotating about an axis parallel with the axis of a tool, e.g. a grinding disc or ring, rotating about a stationary axis, an axially adjustable tailstock spindle parallel and rotating synchronously with the main spindle, a respective centre in the main spindle and in the tailstock spindle, which centres are either of constant eccentricity and exchangeable or are of adjustable eccentricity, a driving device for the workpiece mounted between the centres, further, it has between the driving device and the main spindle a transmission for effecting a positive rotational coupling, with a transmission ratio equal to the number of the polygon, i.e. the number of sides of the workpiece, and in the kinematic chain of the gear mechanism, in the sections of the translational circular movement belonging with the polygonal sides, there is a correcting mechanism which periodically changes the angular velocity.

A further characteristic of the grinding machine according to the invention is that it has an arm angularly displaceable about the axis of the tool e.g. a grinding disc or ring for machining the outer surface of the workpiece which arm forms part of the mechanism for keeping the rotating tool, e.g. the bore stone, for machining the internal surfaces in oscillating motion along a predetermined circular arc, a slide on the arm freely displaceable along the length of the arm, and a second arm which can be rotated about one of its ends that is at the axis of the cylinder of rotation described by the axis of the workpiece, while the other end is secured to the slide so as to be rotatable about the centre point of the latter.

A further characteristic of the grinding machine according to the invention is that it has an arm displaceable perpendicularly to the axis of the workpiece and parallel with the plane covered by the tool, e.g. pottery stone, grinding disc or grinding ring, for machining the outer surface of the workpiece, which arm forms part of the mechanism for keeping the tool, e.g. the bore stone which rotates about its own axis, and which is for machining the internal surfaces, in oscillating motion about a predetermined linear path; and it has on said arm a slide supporting a further arm, the slide being freely displaceable along the length of the first arm, the further arm beng pivotable about the centre point of the slide, and the second arm is rotatable about its other end falling on the axis of rotation described by the axis of the workpiece.

A further characteristic of the grinding machine according to the invention is that it has two forks secured in parallel on the shaft of the tool for machining the outer surfaces, the forks forming part of the mechanism for maintaining the bore stone for machining the internal surfaces in oscillation along a predetermined circular arc, and it has a mandrel projecting into the recess of one of the forks and secured eccentrically on the tail spindle, and further it has a spindle displaceable in the recess of the other fork and holding the bore stone for machining the internal surfaces of the workpiece.

A further characteristic of the grinding machine according to the invention is that is has a tapped spindle for moving the spindle holding the bore stone along the length of the recess of the fork, and a tapped profile coupled to the tapped spindle, and it has a dog clutch for interrupting the positive coupling in the transmission for effecting the rotational positive coupling between the driving device and the eccentric centre.

A further characteristic of the grinding machine according to the invention is that it has, in the transmission which brings about the positive rotational coupling between the drive mechanism and the eccentric centre, a correcting device which has an eccentric journalled in a disc; further, the eccentric has an end projecting into a recess in a disc secured for rotation with a shaft which transmits rotation, via gear wheels, to the main spindle supporting the centre; at the other end of the eccentric there is an arm which is always in contact with the surface of the correcting body; and further, the machine has a threaded spindle for displacing the correcting body along the length of the tubular shaft rotatable in an internal thread in the correcting body and by virtue of that rotation capable of carrying the disc in which the eccentric is journalled.

A further characteristic of the grinding machine according to the invention is that it has in the correcting mechanism, a ring radially deformable by shoes which can be set by screws in any desired angular position relative to a rigid ring which is concentric with a shaft having the same r.p.m. as the main spindle carrying the eccentric centre; in the bore of the deformable ring a disc is secured for rotation with a tubular shaft; an arm rotatable about a pin journalled in the disc; on one end of the arm there is a feeler urged into permanent contact with the surface of the bore of the ring by a spring; further, it has an arm portion which bears against a stop which projects from the other end of the arm and is adjustable by means of a tapped spindle on the disc rotating with the shaft.

A further characteristic of the grinding machine according to the invention is that it has in the correcting mechanism, a helical gear wheel which is mounted displaceably on and for rotation with the shaft for transmitting rotation to the main spindle carrying the eccentric centre, the gear wheel being biased in one direction by a spring; another helical, driving gear wheel meshing with the first gear wheel; a push rod guided in the casting of the main spindle housing and supported by a thrust bearing on the side of the axially displaceable gear which is opposite to the spring; and a ring which is rigidly secured to two diametrically opposite points of the disc secured on and for rotation with, the shaft, the remaining point of the ring being axially deformable by shoes which can be adjusted by screws in any angular position relative to the disc, the ring being in permanent contact with a roller mounted in the push rod and serving as a track for the movement of the roller.

A further characteristic of the grinding machine according to the invention is that it has epicyclic gearing in the correcting mechanism within the transmission bringing about the positive rotational coupling between the main spindle supporting the eccentric centre and the workpiece-driving mechanism, the epicyclic gearing being between the shaft rotating at the rpm. of the main spindle and a tubular shaft concentric with the first shaft and being tiltable about the shaft; and it has a roller rotatable on a shaft projecting from the casing of the epicylcic gearing; further, it has an arm of variable rotational axis one end of which is supported by the roller while the other end bears against the correcting body which is secured on the shaft for rotation therewith. I

A further characteristic of the grinding machine according to the invention is that it has, in addition, an oblique bore formed in a body secured to the end of the main spindle, a centre with a cylindrical shaft journalled in the bore, and a push rod which is coupled to the internal end of the shank of the centre and which is displaceable along the axial direction of the main spindle.

The invention is described in detail with reference to the preferred embodiments of the grinding machine illustrated in the drawings.

FIG. 1 is a diagrammatic illustration of the principle of the preferred grinding machine for carrying out the process according to the invention.

FIG. 2 shows an embodiment of the grinding machine similar to that of FIG. 1, but with the difference that the axis of the workpiece rotates along the cylinder of rotation oppositely to the workpiece.

FIG. 3 is an exemplary scheme of a grinding machine according to the invention wherein machining of the external surface of the workpiece is carried out by a grinding ring, and the workpiece and its axis rotate in the same direction.

FIG. 4 shows an embodiment similar to that of FIG. 3, with the difference that here the workpiece axis and the workpiece rotate in opposite directions.

FIG. 5 is a view parly in elevation and partly in section of an exemplary mechanism for use in practising the scheme shown in FIGS. 1 and 2.

FIG. 6 is a view from another direction of the mechanism shown in FIG. 5.

FIG. 7 is a view of one of the forks of the mechanism shown in FIG. 5.

FIG. 8 is a view of the other form of the mechanism shown in FIG. 5.

FIG. 9 is a schematic view of a centre of continuously adjustable eccentricity.

FIG. 10 is a part-elevation, part-section of a driving mechanism of a construction different from that shown in FIG. 9 and being of a slotted link or fork type.

FIG. 11 is a diagram illustrating the possible profile changes in the case of a triangular shape.

FIG. 12 is qualitative diagram illustrating, for a triangular shape, the changes in the maximum difference t, in the normal direction between the profiles produced with a tool of infinite radius and with a tool of finite radius R FIG. 13 shows an exemplary embodiment of a grinding machine according to the invention wherein the arm carrying the spindle of the bore stone in the case of R 00 performes linear harmonic motion, and the direction of rotation of the workpiece is the same as the direction of rotation of the workpiece axis along the cylinder of rotation.

FIG. 14 shows an embodiment similar to that of FIG. 13, with the difference that the direction of rotation of the workpiece is opposite to the direction of rotation of the workpiece axis along the cylinder of rotation.

FIG. 15 shows a scheme for an exemplary embodiment of the mechanism suitable for guiding the arm supporting the bore stone.

FIG. 16 shows a schematic variant of the mechanism of FIG. 15, using forks.

FIG. 17 is a scheme usable for grinding conical bores and is similar to the mechanism shown in FIG. 5.

FIG. 18 is a scheme of an exemplary embodiment of an insert usable in the mechansim shown in FIG. 17 and enabling the setting of any relative angular position between the oscillating and the rotating components.

FIG. 19 is a diagram illustrating the grinding conditions of points on the profile of minimum and maximum radii, for a rectangular workpiece.

FIG. 20 is a diagram illustrating the grinding conditions of a transitional profile section, between points on the profile of minimum and maximum radii, for a rectangular workpiece.

FIG. 21 is a diagram illustrating a family of curves obtained as a result of grinding with a disc of different diameters.

FIG. 22 is a diagram of an exemplary embodiment of the basic system of a grinding machine according to the invention.

FIG. 23 is a diagram for determining the nature of the auxiliary movements arising in the grinding machine according to the invention, and illustrating the grinding conditions of points of minimum and maximum radii on the profile. 

1. A grinding machine comprising a grinding tool, means for rotating said grinding tool about a fixed axis, means for rotating a polygonal workpiece about its own axis in contact with said driving tool, means for rotating said axis of said workpiece about an eccentric axis at a speed of rotation equal to the speed of rotation of said workpiece about its own axis multiplied by the number of sides of said polygonal workpiece, and a correcting mechanism for changing the angular velocity of rotation of the workpiece about said eccentric axis in those sections of that motion which are associated with the grinding of the sides of the polygon while maintaining constant the speeds of rotation of said grinding tool about said fixed axis and of said worKpiece about its own axis.
 1. A grinding machine comprising a grinding tool, means for rotating said grinding tool about a fixed axis, means for rotating a polygonal workpiece about its own axis in contact with said driving tool, means for rotating said axis of said workpiece about an eccentric axis at a speed of rotation equal to the speed of rotation of said workpiece about its own axis multiplied by the number of sides of said polygonal workpiece, and a correcting mechanism for changing the angular velocity of rotation of the workpiece about said eccentric axis in those sections of that motion which are associated with the grinding of the sides of the polygon while maintaining constant the speeds of rotation of said grinding tool about said fixed axis and of said worKpiece about its own axis.
 2. A grinding machine comprising a grinding tool, means for rotating said grinding tool about a fixed axis, means for rotating a polygonal workpiece about its own axis in contact with said grinding tool, a driven first tubular shaft surrounding and coaxial with a second shaft that rotates said axis of said workpiece about an eccentric axis at a speed of rotation equal to the speed of rotation of said workpiece about its own axis multiplied by the number of sides of said polygonal workpiece, and a correcting mechanism for changing the angular velocity of rotation of the workpiece about said eccentric axis in those sections of that motion which are associated with the grinding of the sides of the polygon, said correcting mechanism comprising a nonrotatable radially deformable ring concentric with said first and second shafts, means for selectively effecting the radial deformation of the ring, an arm carried by said first shaft for rocking about an axis parallel to but spaced from the common axis of said first and second shafts, said arm being biassed against said deformable ring thereby to rock the arm according to the deformation of the ring upon rotation of said first shaft, and means to transmit the rotary and rocking movement of said arm to said second shaft thereby to rotate said second shaft at a variable angular velocity.
 3. A grinding machine as claimed in claim 2, said means for radially deforming the ring comprising shoes that bear against the deformable ring, and a rigid ring in which said shoes are screw-threadedly adjustable in radial directions to adjust the deformation of the ring.
 4. A grinding machine as claimed in claim 2, and spring means urging said arm into contact with said deformable ring. 